Stripper mechanism



April 1961 A. J. DUFFIELD 2,979,188

STRIPPER MECHANISM FIG.

INVENTOR. A. J. DUFFIELD BY Wikw HIS ATTORNEY April 11, 1961 A. J. DUFFIELD 2,979,188

STRIPPER MECHANISM Filed April 14, 1958 2 heets-Sheet 2 I I C1 5 INVENTOR. A. J. DUf-FIELD H15 ATTORNEY United States Patent STRIPPER MECHANISM Albert J. Duflield, Woodbridge, Conn., assignor to Olin Mathieson Chemical Corporation, New Haven, Conn. a corporation of Virginia Filed Apr. 14, 1958, Ser. No. 728,344

1 Claim. (Cl. 205-4) This invention relates to the extrusion of tubular articles, and more particularly to the stripping of drawn articles from a draw punch.

In drawing a tubular article, such as a cartridge case, the cupped-shaped blank is engaged upon a punch and forced through a drawing die of larger diameter than the punch and smaller diameter than the blank so that the wall of the case is drawn to substantially the thickness of the space between the die and the punch. Thereafter, the drawn article is removed from the punch by a stripper mechanism.

An example of such a stripper mechanism is that disclosed in U.S. Patent No. 2,345,857 which comprises a plurality of segmental blocks which are drawn together by means of a retaining spring. When so drawn together the stripper blocks form a collar having a central opening less or approximately equal to the maximum diameter of the punch. The stripper usually has a beveled or a flaring mouth so as to allow the head-end of the drawn case to pass through the stripper plate as it is driven downwardly upon the punch. Upon the upward stroke of the punch the mouth edge of the cartridge case is brought into engagement with the underside of the stripper blocks which hold the drawn article axially fixed while the punch withdraws from the article.

The above-described stripper operates satisfactorily provided the drawing punch is uniformly cylindrical over its entire length. However, in operations wherein the drawing punch performs the additional function of clipping a'predetermined length of the drawn article, the above stripper failed to function in removing the drawn article. This drawing and clipping punch has formed on the upper part of its nose portion a shoulder which closely seats in the annular opening of the die and which shears or pinches off the upper portion of the drawn case as the shoulder passes into the annular opening of the die. A modification of such a drawing and clipping punch and die assembly is shown in US. Patent No. 2,611,475. In these clipping operations the mouth of the clip case remains snugly seated against the clipping shoulder forming a contiguous surface. This prevents the use of the above-described stripping mechanism since the stripper is held open by the clipping shoulder and cannot take hold of the mouth of the drawn piece.

A stripper mechanism capable to a limited extent of removing such tubular cases is shown in US. Patent No. 2,369,187. Briefly, this mechanism consists of an internal plunger within the drawing punch which, when normally retracted, forms a part of the punch operating surface. Upon movement of the punch into the die a means is provided to shift the plunger out of the punch near the end of the stroke to release the tubular case. This type of stripper performs satisfactorily provided the drawing punch is tapered along its entire length. However, when the nose of the drawing punch is cylindrical in whole or in part this stripper fails to function since by the very teachings contained in the last mentioned patent there is a. shrinkage which takes place between the metal case i and the punch so that the case binds itself firmly thereto.

When cylindrical punches are employed in the drawing operation this stripper assembly at most moves the case a small length along the punch, and since the remainder of the punch is cylindrical the drawn case will continue to bind itself on the punch and is failed thereby to be completely removed.

Accordingly, it is the object of this invention to provide a positive stripper means to remove drawn articles from a drawing punch cylindrical in whole or in part of its drawing length.

A further object of this invention is to provide a positive stripping means to remove drawn articles from a drawing punch, cylindrical in whole or in part of its drawing length, having a shoulder abutting the mouth edge of the drawn article.

Other objects and advantages will become apparent from the following description and drawings, in which Figure 1 illustrates an embodiment of the invention showing a cupped blank mounted on a punch just prior to the drawing operation;

Figure 2 illustrates the punch and the drawn article immediately following the shearing of a predetermined length of the drawn case by the clipping shoulder of the punch;

Figure 3 shows the punch at its lowermost position with the stripping plunger beginning the removal of the drawn case from the punch;

Figure 4 shows the punch in its retraction stroke during the partial removal of the drawn case by the secondary stripping means;

Figure 5 is a plane view of the stripper segments of the secondary stripper means; and

Figure 6 is a view taken along lines VI-VI of Figure 5.

Generally speaking, this invention provides a means for removing a drawn cartridge froma punch having a shoulder adjacent and abutting the mouth edge of the drawn article whereby a contiguous surface is formed between the punch and the drawn case preventing the functioning of conventional stripping devices. Such a contiguous surface, between punch and drawn article, is formed when the drawing punch has formed above its nose portion a clipping shoulder which cooperates with the draw die to shear a portion of the drawn case. As a result, the mouth edge abuts the clipping shoulder of the punch. It has been discovered that by partially removing the drawn case from the punch, by means of a plunger mounted in the punch, a sufiicient distance from the shoulder a secondary stripper may be employed against the mouth of the drawn article to completely remove it from the punch.

More specifically, by reference to the drawings, the apparatus, illustrating an embodiment of the invention comprises a die plate 1 provided in its upper surface with a pocket 11 and containing an annular opening 2 from the base of the pocket through to the lower surface of the die plate. Seated in the pocket is a die support plate 4 with a central passage 6, and having mounted thereon die supports 7 and 3 containing annular openings, respectively, 9 and 10. Opening 2 and passages 6, 9 and 10 are of a diameter larger than the outside diameter of the finished drawn article.

A stripper means comprising a stripper holder ring member 12 is seated on die support 8. The ring member is formed wtih a tapered opening 13 tapering inwardly from the bottom to the top of the ring. Within thering opening and supported on the top of die support 8 is disposed a sectional expansion and contraction stripper element 14 consisting of three segment members 64, 65 and 66. Each segment member is provided upon its inner periphery with a downwardly and inwardly tapered inner surface terminating in a punch engaging edge 60 at its lower end. Each segment member is further provided in its outer periphery with a laterally recessed springreceiving groove 16, which, with similar grooves on all segment members, constitute a circnmferentially expanding and contracting groove. Engaged in this groove is a spring member 17 adapted normally to draw the Segment members into their contracted position, as shown in Figure 1, and to permit free expansion of the ring upon passage of the cartridge case or punch as shown in Figures 2 to 4. The outer periphery of the stripper device, surfaces 18 and 19, is tapered inwardly from the bottom to the top at the same angle as the taper of opening 13 of the stripper holder ring 12.

Seated 0n stripper holder member 12 is a draw die 20 having a beveled annular opening 21 merging into a drawing flange 22. The above described assembly is held in place by retaining plate 3 having a circular passage 62 in axial alignment with the opening formed by the draw die land 22. Although only one die is illustrated, it will be understood that a series of such blocks may be employed stacked one on top of another or by die inserts in accordance with standard practice in the drawing of metal tubes.

The illustrated apparatus further comprises a vertically reciprocating ram 23, suitably secured to a conventional power mechanism, not shown, for driving the ram downward, as will be understood by those skilled in the art. Mounted in the ram by means of bushing 24 is a punch holder 25 containing a transverse opening 26. In opening 26 a lever 28 is pivotly mounted at point 53 by means of pin 27. End 49 of the lever projects into the opening 26, while end 48 projects into space to cooperate, in the downward movement of the ram, against a stop 29 fixedly mounted on retaining plate 3.

Mounted in punch holder 25 by means of bushing 59 is a draw punch 30 in axial alignment with the openings defined in the above described die and stripper elements. The draw punch contains an axial passage 31 merging by means of tapered side wall 32 into a smaller axial passage 33. Contained within the punch is an axial plunger 34 consisting of an upper cylindrical body reduced by means of tapered shoulder 36 to a lower cylindrical body 37 of smaller diameter. When shoulder 36 is seated on tapered side wall 32, the dimensions of the upper and lower bodies of the plunger conform to the inner dimensions, respectively, of axial passages 31 and 33. Shoulders 36 and tapered side walls 32 further serve to limit the outward movement of plunger 34. When the lower end 67 of the plunger is flush with the end of the draw punch it forms a part of the end of the punch and the upper end 47 of the plunger protrudes into the transverse opening 26.

Draw punch 30 consists, further, of an upper cylindrical portion 51 reduced by means of tapered shoulder 52 to a relatively smaller cylindrical portion 53. Portion 53 becomes slightly enlarged by means of shoulder 54 into a slightly larger cylindrical portion 55 which is again reduced by means of clipping shoulder 56 into a working nose portion 57. The nose portion consists of a cylindrical portion 58 tapering at point 63 into a tapered former portion 38. The diameters of cylindrical portions 53 and 57, inclusive of portions 58 and 38, conform to the inner dimensions of the drawn case. Enlarged portion 55 has a diameter which approximates the opening defined by draw die land 22.

In operation a cupped blank 44 of brass, aluminum or harder metal, such as obtained by the process detailed in US. Patent 2,630,916, having a side wall 45, a relatively thicker bottom 46 and a flaring scrap ring, or mouth, 43 is brought into axial alignment, month end up, with the punch 30, draw die 20 and stripper element 14. The punch, by any convenient source of power not shown, is brought downward into the cupped blank forcing the closed end of the cupped blank through the die. As the blank is moved through the die, the wall of the blank is drawn, between the punch and the draw die land 22, to a wall thickness substantially equal to the annular space between the punch and the draw die land 22. Because of the particular configuration of the draw punch used for purposes of illustration, the drawn article has cylindrical side wall 40, a thick bottom 42 and an inner tapered portion 41.

As the closed end moves downward below the die, it passes through the stripper element 14 which expands through the expansion of spring 17. Asthe punch descends the clipping shoulder 56 of the punch through cooperation with the die flange 22 shears the scrap ring 43 from the drawn case. It is to be noted, that immediately subsequent to the shearing or clipping operation the mouth edge of the drawn article snugly abuts the clipping shoulder 56 of the punch preventing stripping edge 60 to engage against the drawn article. Since the mouth edge is snugly seated against the clipping shoulder, it forms a contiguous surface with the cylindrical portion 55 of the punch thereof forcing the stripping element to ride over the junction formed by the punch and the case, both, in a downward and upward stroke of the punch.

The punch further descends to bring the cylindrical portion of the punch 55 into the annular opening defined in the stripper element 14. This movement of the punch also brings the tapered portion 52 of the punch against the flaring mouth of scrap ring 43 causing a portion of the scrap ring to extrude into close engagement about the cylindrical portion 53 of the punch.

As the punch nears the end of its downward stroke, a stop 29 cooperates with end 48 of lever 28 to pivot end 49 into cooperation against end 47 of plunger 34 thereby pushing plunger 34 down relative to punch 30. This starts the stripping action by forcing the drawn article down along the cylindrical portion, or working nose portion 57, of the punch.

As the punch starts its upward stroke raising clipping shoulder 56 above the stripping edge 60 of the stripper element, the stripper element engages about the cylindrical portion 57 and against the mouth edge of the drawn article holding the drawn article fixed against any further movement thereby permitting the punch to be Withdrawn from the drawn case. As point 63, which represents the beginning of the taper of the working nose portion of the punch, passes out of the mouth of the drawn article, the drawn article becomes free to drop through openings 10, 9, 6 and 2 respectively, into any convenient collecting means.

The scrap ring 43 may be removed from the punch by any conventional means. For example, the upper portion of the punch may pass through any convenient or suitable aperture, contained in some means fixed against vertical movement, which abuts the mouth of the scrap ring 43 thereby holding and forcing the scrap ring from the punch during the upward movement of the punch.

Although the invention has been described with reference to specific embodiments, materials and details, various modifications and changes will be apparent to one skilled in the art. The invention is, therefore, not to be limited by such embodiments, materials or details except as set forth in the appended claim.

What is claimed is:

A stripper mechanism for deep drawing by means of a drawing punch and die assembly comprising openended draw die, a sectional segmental stripper element fixedly mounted below said die and having an axial opening thcrethrough for receiving the punch and drawn article thereon, mounted in axial alignment with and below the open end of said die, and characterized by plurality of separable circumferentially arranged stripper members assembled as a unitary element adapted to engage with the punch adjacent the mouth edge of the drawn article, means to yieldabl} maintain said segmental members biased inwardly into said engagement as a unitary element, said drawing punch being in axial alignment with said die and with the opening of said stripper element, said punch having a drawing nose portion cylindrical over part of its length formed at the upper end of this drawing nose portion an enlargement substantially as large as said article and forming a clipping shoulder adapted to sever a predetermined length of the drawn article in cooperation with said die, said shoulder after severing abutting the severed mouth edge of said drawn article in substantially flush relationship, means to impart a forward stroke to said punch through said die and into said axial opening of said stripper element to draw said article and to seat said segmental members on said enlargement above the shoulder of said punch, and to further impart a retraction stroke to said punch, an axial plunger slidably mounted in said punch and adapted to project beyond the forward surface thereof, means for causing relative movement between said punch and said plunger during the terminal part of forward stroke, and means determining the coordination of said last named means with the movement of said plunger to actuate the punch after said severing and after said segmental members have seated on said enlargement to break the initial grip of said punch on said article and to move the drawn article along said punch sufliciently to separate the mouth from said shoulder to form a gap which will receive said segmental member in overlying relation to the mouth edge for stripping the drawn article from said punch upon return movement thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,638,995 Hodge Aug. 16, 1927 2,003,438 Guignet June 4, 1935 2,345,857 Newell Apr. 4, 1944 2,369,187 Swertfager Feb. 13, 1945 2,611,475 Slater Sept. 23, 1952 

